Chapter: What Has Been Related About Al-Witr Is Not Incumbent
Ali said: Al-Witr is not incumbent like your obligatory prayers, but it is a Sunnah of Allah's Messenger who said: Indeed Allah is Witr (One), and He loves Al-Witr, so perform Al-Witr O people of the Qur'an.
Sufyan Ath-Thawri and others reported from Abu Ishaq, from Asim bin Damrah, that : Ali said: Al-Witr is not incumbent like the status of the obligatory prayers, but it is a Sunnah which Allah's Messenger practiced.